Strongly correlated exciton-polarons in twisted two-dimensional heterostructures*

In heterostructures of twisted two-dimensional semiconductors the combined effect of the moiré potential and the Coulomb interaction can support the formation of different strongly correlated phases, including charge ordered or Mott localized phases. Yet, identifying the nature of such correlated phases remains a key issue. 

In this seminar, I discuss the excitonic response as a novel tool to unveil the strongly correlated nature of electrons in flat bands of moiré heterostructures. I will present a model description exciton-polarons in combination with the dynamical mean-field theory for strongly correlated electrons in the moiré lattice of a homo-bilayer heterostructure. I will compare the charging diagram of the heterostructure with experimental observations, and show that the exciton-polaron spectrum undergoes a discontinuous evolution as a function of doping with the formation of a double-peak structure for non-integer fillings. I will related the evolution of the exciton-polaron spectrum to the formation of a Mott localized phase, and show that exciton response can provide a direct signature for the formation of correlation driven insulators in gate controlled heterostructures.